Inflammation is the final common pathway of various insults, such as infection, trauma, and allergies to the human body. It is characterized by activation of the immune system with recruitment of inflammatory cells, production of pro-inflammatory cells and production of pro-inflammatory cytokines.
Most inflammatory diseases are characterized by abnormal accumulation of inflammatory cells, including monocytes/macrophages, granulocytes, plasma cells, lymphocytes and platelets. Along with tissue endothelial cells and fibroblasts, these inflammatory cells release a complex array of lipids, growth factors, cytokines and destructive enzymes that cause local tissue damage.
One form of inflammatory response is neutrophilic inflammation which is characterized by infiltration of the inflamed tissue by neutrophil polymorphonuclear leucocytes (PMN), which are a major component of host defense. Tissue infection by extracellular bacteria represents the prototype of this inflammatory response. On the other hand, various non-infectious diseases are characterized by extravascular recruitment of neutrophils. This group of inflammatory diseases includes chronic obstructive pulmonary disease, adult respiratory distress syndrome, some types of immune-complex alveolitis, cystic fibrosis, bronchitis, bronchiectasis, emphysema, glomerulonephritis, rheumatoid arthritis, gouty arthritis, ulcerative colitis, certain dermatoses such as psoriasis and vasculitis. In these conditions neutrophils are thought to play a crucial role in the development of tissue injury which, when persistent, can lead to the irreversible destruction of the normal tissue architecture with consequent organ dysfunction. Tissue damage is primarily caused by the activation of neutrophils followed by their release of proteinases and increased production of oxygen species.
Chronic obstructive pulmonary disease (COPD) is described by the progressive development of airflow limitation that is not fully reversible (ATC, 1995). Most patients with COPD have three pathological conditions: bronchitis, emphysema and mucus plugging. This disease is characterized by a slowly progressive and irreversible decrease in forced expiratory volume in the first second of expiration (FEV1), with relative preservation of forced vital capacity (FVC) (Barnes, N. Engl. J. Med. (2000), 343(4): 269-280). In both asthma and COPD there is significant, but distinct, remodeling of airways. Most of the airflow obstruction is due to two major components, alveolar destruction (emphysema) and small airways obstruction (chronic obstructive bronchitis). COPD is mainly characterized by profound mucus cell hyperplasia.
Cigarette smoking, air pollution and other environmental factors are major causes of the disease. The causal mechanism remains currently undefined but oxidant-antioxidant disturbances are strongly implicated in the development of the disease. COPD is a chronic inflammatory process that differs markedly from that seen in asthma, with different inflammatory cells, mediators, inflammatory effects and responses to treatment (Keatings et al., Am. J. Respir. Crit. Care Med. (1996), 153: 530-534). Neutrophil infiltration of the patient's lungs is a primary characteristic of COPD.
Elevated levels of proinflammatory cytokines like TNF-α, and especially chemokines like IL-8 and GRO-α play a very important role in pathogenesis of this disease. Platelet thromboxane synthesis is also enhanced in patients with COPD (Keatings et al., Am. J. Respir. Crit. Care Med. (1996), 153: 530-534; Stockley and Hill, Thorax (2000), 55(7): 629-630). Most of the tissue damage is caused by activation of neutrophils followed by their release of (metallo)proteinases, and increased production of oxygen species (Repine et al., Am. J. Respir. Crit. Care Med. (1997), 156: 341-357; Barnes, Chest (2000), 117(2 Suppl): 10S-14S).
Most therapeutic endeavour is directed towards the control of symptoms (Barnes, Trends Pharm. Sci. (1998), 19(10): 415-423; Barnes, Am. J. Respir. Crit. Care Med. (1999) 160: S72-S79; Hansel et al., Expert Opin. Investig. Drugs (2000) 9(1): 3-23). Symptoms usually equate with airflow limitation and bronchodilators are the conventional therapy of choice. Prevention and treatment of complications, prevention of deterioration and improved quality and length of life are also primary goals stated in the three key international guidelines for the management of COPD (Culpitt and Rogers, Exp. Opin. Pharmacother. (2000) 1(5): 1007-1020; Hay, Curr. Opin. Chem. Biol. (2000), 4: 412-419). Basically, most of the current therapeutic research has been focused on mediators involved in the recruitment and activation of neutrophils, or attenuation of consequences of their undesirable activation (Stockley et al., Chest (2000), 117(2 Suppl.): 58S-62S).
In 1975, TNF-α was defined as an endotoxin-induced serum factor causing tumor necrosis in vitro and in vivo (Carswell E. A. et al. Proc. Natl. Acad. Sci. U.S.A. 1975, 72, 3666-3670). In addition to antitumor activity, TNF-α has several other biologic activities that are important in homeostasis as well as in pathophysiological conditions. The main sources of TNF-α are monocytes-macrophages, T-lymphocytes and mast cells.
The finding that anti-TNF-α antibodies (cA2) are effective in the treatment of patients suffering from rheumatoid arthritis (RA) (Elliot M. et al. Lancet 1994, 344, 1105-1110) intensified the interest to find new TNF-α inhibitors as possible potent medicaments for RA. Rheumatoid arthritis is an autoimmune chronic inflammatory disease characterized by irreversible pathological changes of the joints. In addition to RA, TNF-α antagonists are also applicable to several other pathological conditions and diseases such as spondylitis, osteoarthritis, gout and other arthritic conditions, sepsis, septic shock, toxic shock syndrome, atopic dermatitis, contact dermatitis, psoriasis, glomerulonephritis, lupus erythematosus, scleroderma, asthma, cachexia, chronic obstructive lung disease, congestive heart failure, insulin resistance, lung fibrosis, multiple sclerosis, Crohn's disease, ulcerative colitis, viral infections and AIDS.
The interest of the scientific community has recently turned towards the immunomodulating and anti-inflammatory activities of the macrolide antibiotics (Journal of Antimicrobial Chemotherapy, 1988, 41, Suppl. B, 37-46).
An ideal immunomodulating agent should be able to suppress the deleterious effects of the inflammatory response, while leaving the protective immune responses intact.
Macrolide antibiotics accumulate preferentially within different cells of subjects, especially within phagocyte cells such as mononuclear peripheral blood cells, and peritoneal and alveolar macrophages. (Gladue, R. P. et al, Antimicrob. Agents Chemother. 1989, 33, 277-282; Olsen, K. M. et al, Antimicrob. Agents Chemother. 1996, 40, 2582-2585). Anti-inflammatory effects of some macrolides have been described in the literature. For example, the anti-inflammatory effects of erythromycin derivatives have been described in J. Antimicrob. Chemother. 1998, 41, 37-46 and WO Patent Application No. 00/42055. Taisho claims further anti-inflammatory erythromycin derivatives modified in positions 3, 9, 11 and 12 (EP 0775489 and EP 0771564). In the patent application WO 02/087596, there is a good description of the anti-inflammatory activity of azithromycin, a known antibacterial agent. Azithromycin derivatives lacking the sugar moieties cladinose and desosamine and having anti-inflammatory activity have been described (Pliva, U.S. Pat. No. 4,886,792). International patent applications WO 04/039821 and WO 04/013153 (Zambon Group) disclose macrolide and azalide derivatives lacking cladinose sugar that exhibit anti-inflammatory but not antibacterial activity.
Anti-inflammatory effects of some macrolides are also known from in vitro and in vivo studies in experimental animal models such as in zymosan-induced peritonitis in mice (J. Antimicrob. Chemother. 1992, 30, 339-348) and endotoxin-induced neutrophil accumulation in rat trachea (J. Immunol. 1997, 159, 3395-4005). The modulating effect of macrolides upon cytokines such as interleukin 8 (IL-8) (Am. J. Respir. Crit. Care. Med. 1997, 156, 266-271) and interleukin 5 (IL-5) (EP Pat. No. 0775489 and EP Pat. No. 771564) is known as well.
Macrolides have proved to be useful in the treatment of inflammatory pathologies such as panbronchiolitis (Thorax, 1997, 52, 915-918), bronchial asthma (Chest, 1991, 99 670-673), and azithromycin in particular has proved effective in improving lung function in patients with cystic fibrosis (The Lancet, 1998, 351, 420).
The administration of macrolides to asthmatics is accompanied by a reduction in hypersecretion and in bronchial hypersensitivity resulting from the macrolides' anti-oxidative and anti-inflammatory interaction with phagocytes and in particular with neutrophils (Inflammation, Vol. 20, No. 6, 1996).